A new method to suppress reverberation Doppler spread based on split-beamforming in the data domain

The narrow band (CW) pulse, as a transmitted signal in active sonar, is a kind of Doppler-sensitive signals so that it's usually used to discriminate between the moving target and reverberation based on speed information. When matched filtering with velocity channels is used on a moving platform, the relative velocity between scatters and the moving platform is influenced by the bearing and ground speed of scatters. This coupling results in Doppler spread of reverberation, making it difficult to detect low-speed targets using speed information. A new method, based on conventional beamforming, matched filter processing and own Doppler nullification (ODN), which introduces phase difference judgment in all velocity channels to suppress echoes from unexpected bearing is presented in order to reduce Doppler spread due to the relation between the speed and bearing. Compared with the conventional method, the new approach can reduce Doppler spread by 70%, identifying low-speed weak targets from strong reverberation.